Shrouded impeller



Patented Mar.' 17,1942

snRoUDED IMrELLER Wilton G. Lundquist, Hohokus, N. J., asslgnor to Wright Aeronautical Corporation, a corporation of New York Application october 1o', 1939, serial 10,298,752

(ci. 23o- 134) This invention relates to improvements in blower' impellers,.being particularly concerned with an impeller construction for engine superchargers in which the air passages are shrouded.

Inthe conventional impeller construction,

varies are integral with and project from a solid backing member, which latter sustains the stress due to centrifugal force. The air passages formed between the vanes are covered on one side by a stationary shroud with respect to which the impeller rotates. When air is being pumped at high velocity, the friction drag of the air against the non-rotating shroud surface has a tendency to upset Athe smooth ow of air through the pas-A sages vand accordingly, it is desirable to provide an impeller in which the air passages are covered by a shroud rotating with the impeller and preferably forming an integral part thereof.

It is an object of this invention to provide an impeller structure in whichthe wallsv of the air passages rotate with the impeller, and a related objectV is to provide a construction capable of adequately sustaining the high centrifugal loading on the impeller occasioned by rotating the includtegral metallic member I which has the general form of truncated cone II at one end, and of a cylinder I2 at the other end, the cylindrical portion of the impeller being at the large diameter endof the conical portion. The end faces are substantially plane, and the impeller is provided with a bore I3 by means of which the impeller may be mounted upon a shaft.

A plurality of air passages I4, in the form of cylindrical drillings, extend from the small end face I8 of the impeller axially therealong and radially outward from the impeller axis, the several axes of the drillings I4 being similarly slanted with respect to the impeller axis, and being offset from the `impeller axis so thatthe drilling and impeller. axes do not intersect. In effect, the envelope of the several drillings comprises a modified hyperboloid surface, and the substantially conical surface II of the impeller is conformed to the envelope of the drillings wherefor said surface actually has a modified hyperboloid form rather than a strictly .conical form. The

drillings I4 issue from the impeller through the cylindrical surface I2.

Where the drillings I4 open to the plane end I6, there is an overlap, defining in general a central entrance annulus to the impeller which comprises a plurality of edges I8 at the intersections of walls of adjacent drillings. These edges act as cups or pockets which better serve to entrain lates as the impeller progresses to larger diameter, zones, whereby centrifugal force from the large diameter portions of the impeller is adequately sustained. At the small diameter end of the impeller, adjacent the end I6, centrifugal force will be relatively small and 'the stresses thereof are adequately assumed by the mass of the materialin the rim clrcumscribing the end openings of the drillings.

In Fig. 3, I show a yfragment of an impeller 20 which is substantially identical with that above `described except that the drillings I4 are provided at their outer ends with tapered counterbores 2l allowing for a smooth increase in exit area in the impeller.

In designing an impeller of this character, the drillings I4 retreat from the direction of rotation and these drillings need not necessarily be cylin- .drical as shown but may be tapered throughout their length, either to provide small diameter entrance openings and large diameter exits or vice versa. If desirable, certain zones of the solid part of the impeller may be routed away to provide greater lightness, suchremoval of material from the impeller being carefully accomplished to maintain adequate strength against centrifugal bursting effects thereon.

The impeller of the invention is readily made from a solid piece such as a forging of strong light alloy, the air passages and conformation of the impeller being obtained through simple turning and drilling operations. Thus perfect balance of the impeller, necessary for high operating speed, is obtained without recourse t'o complex milling, bending, and balancing operations Ywhich are necessary for the older types of impellers.

While I have described my invention in detail in its lpresent preferred embodiment, it will be i on said end face to exit openings on said cylindrical face. 2. A blower impeller comprising a substantially conical frustum having an integral cylindrical part at its larger end, said impeller having a plurality of similarly angled axially straight passages passing from entrance opening on the small end face normal to the impeller axis to exit openings on the larger cylindrical face parallel to the impeller axis.

3. A blower impeller comprising a substantially conical frustum having an integral cylindrical part at its larger end, said impeller having a plurality of similarly angled axially straight passages passing from entrance openings on the small end face normal to the impeller axis to exit openingson the larger cylindrical face parallel to the impeller axis, said` holes comprising bores whose axes are angled relative to the impeller axis, the impeller axis and respective bore axes being spaced from' one another.

4. A blower impeller having the external surface form of a volume of revolution defined by rotating a slanting line about non-intersecting axis, said impeller having a plurality of axially straight holes each parallel to a straight line element of the surface of the impeller and extending from entrance openings on an end face of the impeller to exit openings on a circumferential face o'f the impeller.

5. A blower impeller comprising a truncated conical member including an outer cylindrical portion and a small end face normal to its axis having a plurality of straight drillings starting 'on the smaller end face of the member and ex- 'ing through the member wall at the cylindrical portion thereof, said drillings being so disposed that their axes do not intersect the member axis.

7. A blower impeller comprising a truncated conical member including an outer cylindrical portion and a small end face vnormal to its axis having a plurality of straight drillings starting on the smaller end face of the member and extending axially and radially outwardly and opening through the member wall at the cylindrical portion thereof, said drillings overlapping on the small end face to form intake scoops for entering fluid.

8. A blower impeller comprising a truncated conical member including an outer cylindrical portion and a small end face normal. to its axis having a plurality of straight drillings starting on the smaller end face of the member and extending axially and radially outwardly and opening through the member wall at the cylindrical portion thereof, said drillings diverging outwardly and circumferentially from said smaller end `face to provide therebetween, at large diameters of the4 ing through the member wall at the cylindrical portion thereof, said drillings, at their outer ends, being enlarged inthe form of tapered counterbores.'

- WILTON G. LUNDQUIST. 

